DiscountBase::calculateDiscountPercent

static function calculateDiscountPercent($basePrice, $discount)
{
	$basePrice = (float)$basePrice;
	if ($basePrice <= 0)
		return null;
	$discount = (float)$discount;
	if ($discount > $basePrice)
		return null;

	$result = round(100*$discount/$basePrice, 0);
	if ($result < 0)
		$result = 0;
	return $result;
}